Semiconductor optical package and method

ABSTRACT

Embodiments of the present disclosure are directed to optical packages having a package body that includes a light protection coating on at least one surface of a transparent material. The light protection coating includes one or more openings to allow light to be transmitted to the optical device within the package body. In one embodiment, the light protection coating and the openings allow substantially perpendicular radiation to be directed to the optical device within the package body. In one exemplary embodiment the light protection coating is located on an outer surface of the transparent material. In another embodiment, the light protection coating is located on an inner surface of the transparent material inside of the package body.

BACKGROUND

Technical Field

Embodiments of the present disclosure are directed to semiconductorpackaging for optical devices and methods for making same.

Description of the Related Art

Generally described, optical packages include a package body with one ormore optical devices, such as photodiodes, located within the packagebody. Typically, the package body includes a cover of transparentmaterial, such as glass, for protecting the optical devices. Radiationapproaches an outer surface of the glass at various angles of incidentand travels through the transparent material to the optical devicelocated within the package body.

Some optical packages may include two optical devices that are locatedproximate each other, with each of the optical devices being configuredto receive light at different frequency ranges than the other. This cancreates difficulties as radiation intended for one optical device may beexposed to the other optical device. That is, radiation entering anouter surface of the glass cover at low levels of incident, may bedirected to a neighboring optical device in error, thus affecting theaccuracy of the measurement. In that regard, the differing lightspectrums or frequency ranges may not be suitably isolated fromneighboring optical devices.

This problem is associated with optical packages including singleoptical devices as well, due to radiation entering the glass cover witha low level of incident, which may not go through a filter positionedabove the optical device, thereby passing light to the optical device atan undesired frequency.

BRIEF SUMMARY

Embodiments of the present disclosure are directed to optical packageshaving a package body that includes a light protection coating on atleast one surface of a transparent material, such as glass. The lightprotection coating includes one or more openings to allow light to betransmitted to an optical device within the package body. In oneembodiment, the light protection coating and the openings allowsubstantially perpendicular radiation to be directed to the opticaldevice within the package body. In one exemplary embodiment the lightprotection coating is located on an outer surface of the transparentmaterial. In another embodiment, the light protection coating is locatedis located on an inner surface of the transparent material inside of thepackage body.

In one embodiment, there is provided an optical package comprising asemiconductor substrate having an upper surface. The optical packagefurther includes a first optical device formed in the upper surface ofthe semiconductor substrate and configured to receive radiation at afirst frequency range. The optical package further includes atransparent material having a first surface and an opposite, secondsurface. The transparent material is located over the first opticaldevice. The transparent material further includes a first lightprotection coating located on the first surface of the transparentmaterial. The first light protection coating has an opening located overthe first optical device and has a thickness that is equal to or greaterthan a diameter of the first opening. The light protection coating layeris substantially resistant to radiation at the first frequency.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a cross-sectional side view of an optical package inaccordance with one embodiment.

FIG. 1B is a top plan view of the optical package of FIG. 1A.

FIG. 2 is a side view of a transparent material with a light protectioncoating in accordance with the embodiment of FIG. 1.

FIG. 3 is a cross-sectional side view of the optical package of FIG. 1illustrating exemplary radiation being directed toward the opticalpackage.

FIGS. 4A-4G illustrate a method of making the optical package in FIG. 1in accordance with one embodiment.

FIG. 5 is a cross-sectional side view of another optical package inaccordance with one embodiment.

FIGS. 6A-6D illustrate a portion of the method of making the opticalpackage of FIG. 5 in accordance with one embodiment.

DETAILED DESCRIPTION

FIGS. 1A and 1B show an optical package 10 in accordance with oneembodiment. FIG. 1A is a cross-sectional side view of the opticalpackage 10, while FIG. 1B is a top plan view of the optical package 10.The optical package 10 has a package body 12 that includes a cover 14, abottom substrate 16 having inner surface 18 and outer surface 20, andsidewalls 22.

The sidewalls 22 are secured to the inner surface 18 of the bottomsubstrate 16 by an adhesive material 24. The sidewalls 22 may be anymaterial configured to protect the inner portion of the optical package10. In one embodiment, the sidewalls 22 are a metal material, such asaluminum or a tin-zinc compound. As will be discussed below, the bottomsubstrate 16 may include one or more conductive, semiconductor, and/orinsulative layers.

Inside the package body 12 is a semiconductor substrate 26, such assilicon, that is attached to the inner surface 18 of the bottomsubstrate 16 by an adhesive material 62. A first optical device 30 isformed in a first portion of the substrate 26 and a second opticaldevice 32 is formed in a second portion of the substrate 26. The firstand second optical devices 30, 32 are configured to receive radiationand to generate an electrical signal in response to the receivedradiation. In some embodiments, the optical devices are photodiodes.

The electrical signals generated by the first and second optical devices30, 32 may be provided to an integrated circuit (not shown) formed inthe bottom substrate 16. In that regard, conductive paths are providedbetween the first and second optical devices 30, 32 and the integratedcircuit. In the illustrated embodiment, the conductive paths includeconductive wires 34 that are coupled at one end to one or more bond padsof the first optical device and/or the second optical device and atanother end to the bond pads of the inner surface of the bottomsubstrate 16 of the package body 12. Conductive traces or conductivethrough-vias 40 may provide electrical connection between the contactpad on the inner surface of the bottom substrate 16 and the integratedcircuit. Lands 42 on the outer surface 20 of the bottom substrate 16provide electrical connection outside of the package body 12. It is tobe appreciated that in other embodiments, the integrated circuit may belocated inside the package body 12 on the inner surface 18 of the bottomsubstrate 16 or externally connected to the outside of the package 10.

The first optical device 30 and the second optical device 32 receiveradiation at different frequency ranges. For instance, the first opticaldevice 30 may be configured to receive radiation in the visible lightfrequency range, such as a photodiode comprising an ambient lightsensory (ALS) array, and the second optical device 32 may be configuredto receive radiation in the infrared frequency range, such as aphotodiode comprising an RTN single-photon avalanche diode (SPAD) array.

Although the first and second optical devices 30, 32 are shown as beingformed in the same substrate, it is to be appreciated that the firstoptical device 30 may be formed in a substrate that is distinct from thesecond optical device 32. Furthermore, in an alternative embodiment, thesubstrate that forms the bottom substrate 16 of the package includes thefirst and second optical devices 30, 32 and the sidewalls 22 are secureddirectly to the upper surface of substrate 26.

Located above the first and second optical devices 30, 32 of thesubstrate 26 is the cover 14. The cover 14 includes a transparentmaterial 44 that is configured to protect the first and second opticaldevices 30, 32. In one embodiment, the transparent material 44 is aglass material. The transparent material 44 includes a first surface 46facing outwardly of the package and an opposite, second surface 48facing the first and second optical devices 30, 32. In the illustratedembodiment, the second surface 48 of the transparent material 44 islocated a distance from the upper surface of the substrate 26, thuscreating a cavity in which the conductive wires 34 are located. However,it is to be appreciated that second surface 48 of the transparentmaterial 44 may be secured to the upper surface of the substrate 26 byan adhesive, or it may directly rest on top of the upper surface of thesubstrate 26. In such an embodiment, the first and second opticaldevices 30, 32 may be coupled to the integrated circuit in the bottomsubstrate 16 by through-vias through the substrate 26.

A first light filter 50 is located on the first surface 46 of thetransparent material 44 over the first portion of the substrate 26 suchthat the first light filter 50 is located over the first optical device30. A second light filter 52 is located on the first surface 46 of thetransparent material 44 over the second portion of the substrate 26 suchthat the second light filter 52 is located over the second opticaldevice 32. The first and second light filters 50, 52, respectively, areconfigured to pass light that corresponds to the type of the light eachof the respective first and second optical devices 30, 32 is configuredto receive. For instance, in an embodiment in which the first opticaldevice 30 includes an ambient light sensor (ALS) array, the first lightfilter 50 may be configured to pass visible light. In an embodiment inwhich the second optical device 32 is a single-photon avalanche diode(SPAD), the second light filter 52 may be configured to pass infraredlight.

A light protection coating 56 is located on at least one of the firstand second surfaces 46, 48 of the transparent material 44. In theillustrated embodiment, the light protection coating 56 is located onthe first surface 46 of the transparent material 44. Generallydescribed, the light protection coating 56 is made from a lightabsorbent material. In that regard, the light protection coating 56absorbs a significant portion of the light directed toward. In addition,the light protection coating may be configured to reflect light directedtoward it. In one embodiment, the light protection coating 56 isconfigured to absorb and/or reflect over 90% of the IR radiationdirected toward its surface. Furthermore, the light protection coating56 is configured to minimize radiation refracting in the transparentmaterial 44. In some embodiments, the light protection coating 56 is adry film, such as photoresist or an organic polymer.

The light protection coating 56 has openings 58 above the first andsecond optical devices 30, 32 to allow light to be received through thecorresponding filters and be directed to the optical devices 30, 32.Although the openings 58 in the illustrated embodiment are a circlehaving a diameter as best shown in FIG. 1B, the openings 58 may be anyknown shape and the term diameter may thus refer to a width or adiagonal width of the shape of the opening 58. For example, the shape ofthe opening 58 may be a square and the diameter may thus refer to asidewall of the square or the diagonal dimension of the square.

FIG. 2 shows a side view of the transparent material 44 with the lightprotection coating 56 without the other portions of the optical package10. As shown in FIG. 2, the light protection coating 56 has a thicknessthat is substantially equal to the diameter of the openings 58. In oneembodiment, the thickness of the light protection coating 56 and thediameter of the openings 58 is between about 300 to 400 microns. It isto be appreciated that in other embodiments, the thickness of the lightprotection coating 56 may be greater than the diameter of the openings58. In yet another embodiment, the thickness of the light protectioncoating 56 is less than the diameter of the openings 58.

FIG. 3 illustrates exemplary radiation rays being directed toward theoptical package 10. Ray A is directed at an angle toward package at alow level of incident and is absorbed by the light protection coating56. Although not shown, ray A may also be reflected, at least in part,by the light protection coating 56. Similarly, if radiation enters theopening 58 having a low level of incident, the radiation may be directedinto the sidewalls of the light protection coating 56 at the opening,thereby absorbing and/or reflecting light away from the optical devices30, 32 located below. For instance, ray B enters the opening 58 with alow level of incident and is absorbed by the light protection coating56, thus preventing ray B from being directed to the second opticaldevice 32. The light protection coating 56 and the openings 58 allowradiation having a high level of incident to be provided to the opticaldevices 30, 32. For instance, ray C is directed toward one of theopenings 58 in the light protection coating 56 and at least a portion ofray C goes through the second light filter 52 and is provided to thesecond optical device 32.

FIGS. 4A-4G illustrate various stages of making the optical package 10in accordance with one embodiment. As shown in FIG. 4a , first andsecond filters 50, 52 are placed on the first surface 46 of thetransparent material 44 in a spaced-apart relationship. The size of thefirst and second filters 50, 52 may correspond to the radiationreceiving portion of the first and second optical devices 30, 32 or maybe larger than the radiation receiving portion of the first and secondoptical devices 30, 32.

The light protection coating 56 is deposited on the first and secondsurfaces 46, 48 of the transparent material 44 as shown in FIG. 4b . Inone embodiment the light protection coating 56 is photoresist, and thephotoresist is deposited on the transparent material using knowndeposition techniques.

As shown in FIG. 4C, openings 58 are formed in the light protectioncoating 56, such as by etching or exposure, developer, and curingtechniques. It is to be appreciated, however, that the light protectioncoatings 56 may be deposited on portions of the first surface 46 suchthat openings 58 are formed during the deposition process itself. Asshown in FIG. 4D, the structures are then singulated at the location ofarrow A into separate structures, such as by sawing or laser techniques,to form the cover 14.

As shown in FIG. 4E, the transparent material 44 is then coupled at itsside surfaces to the sidewalls 22 of the package body 12. In oneembodiment, the sidewalls 22 may be secured to the side surfaces of thetransparent material 44 via an adhesive material (not shown). In anotherembodiment, the sidewalls 22 may be secured to the transparent material44 during an injection molding process. That is, the covers 14 areplaced into the mold and the sidewall material is injected into themold. The injected sidewall material hardens against the transparentmaterial 44 and the light protection coating 56.

As shown in FIG. 4F, the substrate 26 is secured to the bottom substrate16 via an adhesive material 62. The adhesive material 62 may be athermally conductive paste or an insulative paste. One or moreconductive wires 34 are coupled at one end to the bond pads of one ofthe first and second optical devices 30, 32 and at another end to thepads of the bottom substrate 16.

As shown in FIG. 4G, the sidewalls 22 are secured to the inner surface18 of the bottom substrate 16 via the adhesive material 24, therebyforming the optical package 10. The adhesive material 24 may be athermally conductive paste or an insulative adhesive material.

FIG. 5 shows a cross-sectional view of an optical package 10 a inaccordance with a second embodiment. The optical package 10 a isidentical to the optical package 10 of FIG. 1 except the optical package10 a of FIG. 5 has a cover 14 a that includes a second light protectioncoating 56 a on the second surface 48 of the transparent material 44. Asshown in FIG. 5, radiation ray D is directed toward the opening 58 ofthe light protection coating 56 on the first surface 46 of thetransparent material 44 at an obtuse angle. Ray E enters the transparentmaterial 44 and is reflected, at least in part, by the second lightprotection coating 56 a on the second surface 48 of the transparentmaterial 44 as shown by ray F. Furthermore, some of the ray E may beabsorbed by the second light protection coating 56 a.

Furthermore, at least a portion of the radiation directed to the lightprotection coating 56 may be allowed through the light protectioncoating 56 on the first surface 46 of the transparent material 44, suchas an amount less than 10%. The second light protection coating 56 a onthe second surface 48 of the transparent material 44 would be able toreflect and/or absorb this radiation. As such the reflected radiationmay travel through the transparent material 44 and may be directed tothe light protection coating 56 on the first surface 46, which also mayreflect and/or absorb the radiation. In that regard, the radiation maysuitably dissipate before reaching the opening 58 in the second lightprotection coating 56 a above the second optical device 32.

The first and second light protection coatings 56, 56A of the package 10a further cause the radiation directed to the first and second opticaldevices 30, 32 to be even more vertical than the package 10 of FIG. 1.

FIGS. 6A-6D illustrate a method of making the cover 14 a for the opticalpackage 10 a of FIG. 5. The method of FIGS. 6A-6D are the same as themethod of FIGS. 4A-4D except that a second light protection coating 56 ais also deposited onto the second surface 48 of the transparent material44. As shown in FIG. 6c , openings 58 are formed in the light protectioncoatings 56, 56A on both first and second surfaces 46, 48 of thetransparent material 44. Although not shown, it is to be appreciatedthat in another embodiment the light protection coating 56 a may belocated on the second surface 48 of the transparent material 44 and notlocated on the first surface 46 of the transparent material 44.

The optical packages can be used in a variety of optical devices, suchas cameras, smart phones, or any other optical device.

It is to be appreciated that the term light and radiation have been usedinterchangeably herein.

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

The invention claimed is:
 1. An optical package comprising: asemiconductor substrate having a first surface and an opposite secondsurface; a first optical device configured to receive radiation at afirst frequency range, the first optical device being formed in a firstportion of the semiconductor substrate between the first and secondsurfaces; a transparent material having a first surface and an oppositesecond surface, the transparent material being aligned with andoverlapping the first optical device, the first surface of thesemiconductor substrate being between the second surface of thetransparent material and the second surface of the semiconductorsubstrate; and a first nontransparent light protection coating formed onthe first surface of the transparent material, the first nontransparentlight protection coating having a first opening aligned with andoverlapping the first optical device, the first opening allowingradiation at the first frequency range to travel to the first opticaldevice, the first nontransparent light protection coating having athickness that is equal to or greater than a diameter of the firstopening.
 2. The package of claim 1 further comprising a secondnontransparent light protection coating formed on the second surface ofthe transparent material, the second nontransparent light protectioncoating having a first opening that is aligned with the first opening ofthe first nontransparent light protection coating.
 3. The package ofclaim 2, further comprising a second optical device configured toreceive radiation at a second frequency range, the second optical devicebeing formed in a second portion of the semiconductor substrate betweenthe first and second surfaces, the first nontransparent light protectioncoating having a second opening aligned with and overlapping the secondoptical device, the second opening being equal to or less than thethickness of the first nontransparent light protection coating, thefirst nontransparent light protection coating being resistant toradiation at the second frequency range.
 4. The package of claim 3wherein the first frequency range is within the infrared spectrum andwherein the second frequency range is within the visible light spectrum.5. The package of claim 4 further comprising an infrared pass filterformed on the first surface of the transparent material and positionedbetween the transparent material and the first nontransparent lightprotection coating, a portion of the infrared pass filter being alignedwith and overlapping the first opening of the first nontransparent lightprotection coating and a visible light filter formed on the firstsurface of the transparent material and positioned between thetransparent material and the first nontransparent light protectioncoating, a portion of the visible light filter being aligned with andoverlapping the second opening of the first nontransparent lightprotection coating.
 6. The package of claim 1 wherein the thickness ofthe first nontransparent light protection coating is between about 300microns to 400 microns.
 7. The package of claim 1 wherein the firstnontransparent light protection coating is a polymer or photoresist. 8.The package of claim 1 wherein the second surface of the transparentmaterial is proximate the first optical device.
 9. The package of claim1 wherein the transparent material is glass.
 10. An optical packagecomprising: a semiconductor substrate having a first surface and anopposite second surface; a first optical device formed in a firstportion of the semiconductor substrate between the first and secondsurfaces, the first optical device being configured to receive radiationat a first frequency range; a second optical device formed in a secondportion of the semiconductor substrate between the first and secondsurfaces, the second optical device being configured to receiveradiation at a second frequency range that is different from the firstfrequency range; a transparent material having a first surface and anopposite second surface, a first portion of the transparent materialbeing aligned with and overlapping the first optical device and a secondportion of the transparent material being aligned with and overlappingthe second optical device, the first surface of the semiconductorsubstrate being between the second surface of the transparent materialand the second surface of the semiconductor substrate; a first opticalfilter formed on the first surface of the first portion of thetransparent material and a second optical filter formed on the firstsurface of the second portion of the transparent material; and a firstnontransparent light protection coating formed on the first surface ofthe transparent material, the first nontransparent light protectioncoating having a first opening aligned with and overlapping the firstoptical device and a second opening aligned with and overlapping thesecond optical device, the first optical filter being between thetransparent material and the first light protection coating.
 11. Theoptical package of claim 10 wherein the first nontransparent lightprotection coating has a thickness that is equal to or greater than adiameter of the first and second openings.
 12. The optical package ofclaim 10 wherein the second surface of the transparent material isproximate the first and second optical devices.
 13. The optical packageof claim 10 wherein the first optical filter is an IR pass filter andthe second optical filter is a visible light pass filter.
 14. Theoptical package of claim 10 wherein portions of the first and secondoptical filters are covered by the first nontransparent light protectioncoating and are between the transparent material and the firstnontransparent light protection coating.
 15. A method of forming anoptical package comprising: positioning a transparent material over on afirst surface of a semiconductor substrate that includes a first opticaldevice formed in a first portion of the semiconductor substrate, thefirst optical device being configured to receive radiation at a firstfrequency, the transparent material aligned with and overlapping thefirst optical device; and forming a first nontransparent lightprotection coating on a first surface of the transparent material;forming a first opening through the first nontransparent lightprotection coating, the first opening aligned with and overlapping thefirst optical device, the first nontransparent light protection coatinghaving a thickness that is equal to or greater than the first opening.16. The method of claim 15 wherein forming the first opening includesdepositing or coating the first surface of the transparent material withthe first nontransparent light protection coating and removing portionsof the first nontransparent light protection coating.
 17. The method ofclaim 15 wherein forming the first nontransparent light protectioncoating includes forming a second opening in the first nontransparentlight protection coating, the method further comprising forming a secondnontransparent light protection coating having third and fourth openingson a second surface of the transparent material, the third and fourthopenings of the second nontransparent light protection coating beingaligned with the first and second openings of the first nontransparentlight protection coating, the second nontransparent light protectioncoating having a thickness that is equal to or greater than the thirdand fourth openings in the second nontransparent light protectioncoating.